Method of mounting electrodes



May 7, 1935.

METHOD OF MOUN TI NG ELEC TRODE S Filed Aug 4, 1934 1 i a2 39 52 I wvewrok ku-5530 I I 32 as 24 2, 04mm 1M ATTORNEY J. E. CLARK 2,000,163

Patented May 7, 1935 .1 I I I i METHOD OF MOUNTING ELECTRODES JamesE. Clark, Long Island City, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of'New York Application August 4, 1934, Serial No. 738,422 6 Claims. (c1. 250-215) This invention relates to methods of mountremoved from the arbors and the inner grid is ing electrodes of electron'discharge' devices, and stretched or tensioned to a de u en to more particularly. to the mounting. of dual grids i du e a pe mane t Set in t e late al tu ns but of multi-electrode discharge devices. 7 suflicient to conform the lateral turns to a UNITED STATES PATENT-OFFICE An object of this invention is to secure acp a ti p and pa s that th 5 curate and uniform space relationship between grid may be inserted within the lateral turns of the lateral wires of two grid electrodes of closed the Outer grid- When t at l u ns o the formation arranged in coplanar 1 3 1 wit inner grid are positioned in alternate relation other cooperating electrodes in electron dis with the lateral turns of the outer grid the ten-' charge. devices. I

a In power type electron discharge devices,:1ow grid laterals assume their initial bowed form beinternalimpedance between the electrodes is a tween h laterals 0f the Outer d- The fina prime requisite for operating efiiciency. This Operation Consists in app y en on to Oneor impedance is easily obtained in three-electrode both E ,b particularly to the inner grid, to

15 devices when thegridand anode are formed of Such a degree as to produce a. p a ent et in 15 flattened cylinders with the largest areas'thereof the laterals Of this, grid whereby h e ate a s close to an energized electrode, such as a theriare spaced apart exactly the same as the laterals mionically active cathode, arranged in a central 0f the Outer grid- This i p o uced on an arbor plane surrounded by the grid and the anode. insure accurate alignment of o g id Obviously, h th grid is interposed Ilhese and other features of the invention will 20 the discharge path between the cathode and the be more clearly understood from t e followin anod th impedance is increased by t g detailed description taken in connection with the the anode further avray from the cathode, unless panying drawin in which:

the second grid occupies the same planar posi- Shows a Plan View of the winding form tion as the original grid. Usually, the grids are. of the inner grid; r I 25 helically wound on support rods and this struc- 2 1S plan of a composite arrange ture, while most efiicient for o erati ment of the inner and outer grids illustrating manufacturing p r se presents certain m; in dotted lines the original form of the inner culties when it is desired to intermesh twosimigrid as Shown in e 1 and its equent form sov lar grids so that the lateral wires of one ofthe when Stretched and placed within t e ute 0 grids alternate in the same plane with the lateral grid; wires of t other grid; I I Fig. 3 is similar to Fig. 2 but illustrates a pla According to one aspect of this invention, th View of the two grids after the nne grid'is two grids are accurately aligned in coplanar reintermeshed with the Outer grid and they te lation by a method of assembly which'insures sionfis rhleased;

positive parallel relationship between the indi 4 Illustrates a plan v w f the finalfor vidual, lateral turns of the two grids when ofth'e two grids after stretching with the lateral mounted in permanent position. The method of Winis of both grids in o m parallel planes; fabrication consists in winding the two gridsas 5 is a perspective view of the type of 0 separate units, placing one within the other so arbor or m upon which the inner d 18- their lateral turns alternate and then stretching Wound; a or tensioning the grids along one dimension on 156 illustrates the Stretching apparatus o a form or arbor to a point just beyond their tensioning the grid tu s; elastic limits. This stretching brings the lateral 7 is a r c ive View of a discharge desion on the inner grid is released and the inner 10. p

turns of both grids in contact with both sides of Vice embodying the dual grid Structure Of 5."

t arbor and t degree of tretching insures invention with a portion of the enclosingvessel f apermanent set in the lateral turns so that they and the anode broken away to Show the a remain parallel when the tension and arbor are Tangement 0f the grids; and removed Fig. 8 is a cross-sectional view on the line According to a more specific method of this of W g t e relationship 0f the invention, the inner grid, or the grid having the dual grids with respect to the cathode and anode i smaller dimensions, is wound on an oval arbor 0f the device. a

so that the lateral turns have an initial bowed Thisinvention pertains to the type. .of grid form, while the outer grid is woundona .flat' electrode in which a plurality of closely spaced 5 arbor. ;In order to assemble the grids, they. are wire loops of substantially rectangular shape,

are arranged on two parallel rigid wires which form upright supports for the grid, the center portions of the short sections of each loop being welded or secured to the upright supports. Usually this type of grid is Wound on an arbor or form having the desired configuration of the finished grid with the supporting wires held in grooves at opposite sides of the arbor and the fine wire wound around the arbor and the supports, the laterals of the fine wire grid being uniformly and accurately spaced with respect to the pitch of winding of the fine wire and the that the distance between centers of the support axial line of the grid configuration.

When it is realized that the control characteristics of a discharge device, such as asdeteotor or an amplifier, are determined by the relative spacing of the grid laterals and their relation with respect to the associated electron source and the anode in the device, it is evident that any distortion of the grid laterals will cause irregular control action in the device andfail to. attain the highest efficiency for the operation of the device. Furthermore, in view of the fact that the .fiattened cylindrical form of grid is the most efficient configuration from a manufacturing and operating standpoint in high power devices, it is evident that this configuration does not readily permit its adaptation to a coplanar structure in which two grids are arranged in such a manner that their laterals are equidistant from opposite sides of the cathode and the anode of a discharge device.

According to this invention, a method of mounting two coplanar grids of the flattened cylindrical form is set. forth and the various steps of combining these grids into a single unit is shown in Figs. 1 to 4, inclusive, in which A represents the outer gridand B represents the inner grid. The grid A is wound on a metallic arbor or form having flattened sides with a pair of parallel supporting wires l positioned in the grooves at opposite edges of the arbor and a fine wire I! wound continuously and evenly spaced around the support wires l0 and the arbor which is rotated. Since the various operations in the mounting of the two grids in accordance with this invention depends on minute variations in dimensions, which are not readily apparent from the figures in the drawing, it will clarify the understanding of this invention if reference is made to the actual measurements and materials and the specific series of operations in forming the grid structuresin accordance with one embodiment of the. invention. For instance, the support wires may be made of .040 inch nickel wire about 2% inches long. These are placed in the grooves one flat arbor having a thickness such that the distance between the inner surfaces of the wire H, which may be of .005 inch molybdenum is .110 inch. The wire H is wound around the arbor and. the support wires H) with a pitch of 12.9 turns per inch and a total of 25 turns are wound to form the grid structure. The width of the grid from center to center of the support wires I0 on the arbor is ,.874 inch. After the grid turns are secured to the support wires 10 by any suitable means, such as welding, the completed grid is removed from the arbor and placed on a split arbor l2 shown in Fig. 6 which forms a removable part ofv the stretching device l3.

This device consists of a base having a lever l4 secured to a pivoted plunger I5 which is connected at one end to a lever beam I6 attached to a spreader member I]. A spring 18 held inc.

socket of the base of the device engages a disc I9 attached to the pivoted plunger l5 to return the lever M to a normal position after depression thereof. The split arbor I2 consists of a rigid section 20 and a yielding section 2|. The yielding section 2| is caused to move away from the stationary section 20 by the upward movement of the spreader. member I! which enters the space between the rigid section 20 and the yielding section 2| of the arbor. The grid A after winding is placed on the split arbor l2 and stretched to just beyond its elastic limit so wires I0 is changed from .874 inch to .900 inch. This stretching is performed to insure exact laterality between the consecutive turns of the fine wire on the supports.

The inner gridB is Wound on an arbor 22 having a substantially oval configuration as shown in Fig. 5. The support wires 23 of this grid may be formed of .040 inch nickel wire and have a length of 21 11 inches. These wires are placed in the grooves at opposite edges of the ar bor 22, the distance between centers of thesupports being .702 inch and the distance between the edges C of the arbor 22 being 11/64 inch A molybdenum wire 24 having a diameter of .005 inch is wound around the arbor 22 and the supports 23 with a pitch of 12.9 turns per inch and a total of 25 turns to complete the winding of the inner grid B. The fine wire 24 is secured to the supports 23 by welding the wireto-the supports at the contacting points therebetween. The inner grid B is removed from thearbor 22 and placed on a split arbor in the stretching device l3, the portions of the split arbor being changed, however, for this grid, since it'is not intended to stretch the grid B to its final set form in this operation. Therefore the shape of the portions of the split arbor are such that it is relatively thin and merely engages the surfaces of the supports 23 and does not engage the lateral sections of the grid. Pressure is then applied to the lever I4 to stretch the grid B to such a form, as shown in Fig. 2 in solid line, that the laterals are brought parallel to'each other and the dimension between the surfaces of the laterals is .093 inch inside. This stretching, however, is not carried to the extent of the elastic limit of the'wire and therefore the deformation of the grid Bis not a final set condition. When the inside dimension of .093 inch is secured between the laterals of the grid B the previously stretched A grid is very carefully advanced over the grid B toenvelop it until the grid laterals of the grid A alternate with the grid laterals of the grid B. When this relationship is attained the stretching pressure is released and the grid B assumes a position as shown in Fig. 3 in which the laterals of the grid B revert to substantially their original bowed form but these laterals are arranged in alternate relation between the laterals of the grid A.

After the composite grid structure is removed from the stretching device the sections of the split arbor are changed to substitute sections having. a thickness equal to the width of the grid A, namely, .110 inch. After these sections are secured in position the two grids are threaded over the split arbor, the arbor being situated in the central portion of the confines of the two grids; Pressure is then applied to the lever I4 to stretch the inner grid B to just beyond the elastic limit of the fine wire 24 and the grid B is stretched from itsoriginal width between centers of "the 'isiimiorts-v 2:, namely, .702 inch :to .:.*120. inch." This stretching operationincombination with the diameter of the split arborz425setsthe laterals of the grid B to the samadiameter 101 the grid'A, namely, .110: inch. 'Ihepressurei-is relieved by releasing the leverll andxthe; two grids are removed from the arbor in a condition a'sshown in Fig. 4 which is the final operation in forming the grids. It will be seen from Fig. 4 that the grid laterals of the grid B are coplanar with the laterals of the grid A and the stretching operation insures that the laterality of the adjacent wires of both grids is accurate and uniform and consequently the laterals of both grids will be in coplanar relation with respect to other cooperating electrodes in a device such as shown in Fig. 7.

This device comprises an enclosing vessel 25, highly evacuated, and provided with an inwardly projecting stem 26 which supports a number of pairs of bent wires 21, 28 and 29 and a central wire 39. The stem 26 also supports a clamping collar 3| which carries four upright rods 32 which enter longitudinal grooves in a stamped box-shaped metallic anode 33. Two of the supports 32 carry a pair of metallic clips which fasten a semicircular mica disc 34 thereto, the disc having a wedge-shaped cut-out portion in the center thereof. A pair of narrow metallic strips 35 and 36 are clamped to the narrow width of the mica disc 34 and extend in a parallel direction from the periphery of the disc toward the longitudinal edge of the wedge-shaped cutout portion. These strips are secured in position by the upturned ends of the strips which are registered in notches cut in the periphery of the disc and the longitudinal edge of the cutout portion. The ends of the strips adjacent the periphery of the disc extend at an upward angle and two parallel resilient wires 40 and 4| are secured at one end to the upturned ends of the strips 35 and 36, respectively. The free ends of the wires 40 and 4| carry downwardly extending hooks 31 and 38 which engage the bights of an M-shaped ribbon filament 39, which is arranged in a central plane of the anode 33 with the free ends of the filament attached to the pair of bent wires 29 in the stem and the midportion attached to the straight wire 30.

The coplanar grids, made in accordance with this invention, surround the filament 39 and are equally spaced with respect to the filament and the anode 33 by having the lower ends of the support wires of the outer grid A rigidly secured to the bent wires 21 in the stem and the upper ends registered in an aperture at one side of the disc 34 and in a slot at the other side of the disc. The support wires 23 of the inner grid B are secured at the lower end to the bent wires 28 and at the other end are registered in an aperture in alignment with the support wire I!) of the outer grid at one side of the disc and arranged in the slot adjacent the support wire In on the other side of the disc. This assembly permits the grids to expand and contract during operation but maintains them in coplanar relation, as shown in Fig. 8, with respect to the filament 39 and the anode 33. Furthermore, the laterals of both grids on opposite sides of the filament are accurately aligned in a vertical direction and are uniformly spaced laterally with respect to each adjacent turn of the grids due to the positive stretching method of this invention in forming the grids.

While the various steps of forming the grids heretofoine; described specify; the fstretchingof the grids; individually, it is; of j'course, understood thatbothlgrids may be finally stretched together in one. operation. Furthermore; the invention ;is

not limitedftothe specificLformpf-theflattened cylindrical grid nor to the originalrelative shape ofv the two grids before. stretching. Therefore, thevmethods this: invention are .only to... be limited within the scope of the appended claims.

What is claimed is:

1. The method of assembling hollow grids for discharge devices which comprises forming an inner and an outer grid, placing the inner grid within the outer grid with the laterals in alter-. nate relation, and stretching the grids to a point beyond the elastic limit to secure a permanent set in the laterals, whereby the laterals of one grid will be in the same plane as the laterals of the other grid.

2. A method of fabricating grids of the enclosed type which comprises winding two grids separately, one of the grids having a form in which the diameter in one direction is less than that in a transverse direction, the other grid having an oval form in which the smaller diameter is greater than the lesser diameter of the first grid and the larger diameteris smaller than the larger diameter of the first grid, expanding the second grid along its larger diameter, introducing the expanded grid into' the first grid, equalizing the position of one'of the grids to locate the laterals thereof intermediate the laterals of the other grid, permitting the expanded grid to return to its original form, elongating the oval grid, and gauging the smaller dimension thereof to the lesser dimension of the other grid.

3. A method of assembling wire wound grids for discharge devices which comprises winding an inner grid on an oval arbor, winding an outer grid on a flat arbor, removing thearbors, initially tensioning the inner grid, placing it within the outer grid while in a stretched condition, positioning the laterals of the inner grid in alternate relation to the laterals of the outer grid, releasing the tension on the inner grid so the laterals thereof return to the original oval form, inserting a flat arbor within the boundaries of both grids, and finally stretching at least the inner grid to substantially the elastic limit of the wire to conform the laterals of both grids to a permanent position against the faces of the arbor.

4. A method of correlating two grids of the continuous wound type which comprises winding a wire grid of rectangular formation, stretching said grid to set the laterals thereof, winding a second wire grid with 'bowed sides, exerting internal pressure on said second grid at right angles to the bowed sides, inserting the second grid within the boundary of the rectangular grid, relieving the pressure on said second grid when the turns thereof are positioned in relation between the turns of the rectangular grid, and finally straightening the bowed sides of said second grid in substantial alignment with the sides of said rectangular grid.

5. A method of correlating two grids of the continuous wound type which comprises winding a wire grid of rectangular formation, winding a second grid form with bowed sides, temporarily reducing the thickness of the second grid form to a degree less than the thickness of the recprises stretchirig" one grid to just beyond its elastic limit; stretching a, second grid to a point below its elastic limit, placing the second grid within thefl'rst grid, then threading the second grid into the first grid andth'ereafter stretching the second grid to just beyond its elastic limit.

JAMES E. CLARK. 

